Monte Carlo Program Research Articles

MCmatlab: an open-source, user-friendly, MATLAB-integrated three-dimensional Monte Carlo light transport solver with heat diffusion and tissue damage.

While there exist many Monte Carlo (MC) programs for solving the radiative transfer equation (RTE) in biological tissues, we have identified a need for an open-source MC program that is sufficiently user-friendly for use in an education environment, in which detailed knowledge of compiling or UNIX command-line cannot be assumed. Therefore, we introduce MCmatlab, an open-source codebase thus far consisting of (a)a fast three-dimensional MC RTE solver and (b)a finite-element heat diffusion and Arrhenius-based thermal tissue damage simulator, both run in MATLAB. The kernel for both of these solvers is written in parallelized C and implemented as MATLAB MEX functions, combining the speed of C with the familiarity and versatility of MATLAB. We compare the RTE solver to Steven Jacques' mcxyz, which it is inspired by, and present example results generated by the thermal model. MCmatlab is easy to install and use and can be used by students and experienced researchers alike for simulating tissue light propagation and, optionally, thermal damage.

Gamma-ray shielding properties for silicate glasses containing Bi2O3, PbO, and BaO

Introduction: With the extensive application of radiation sources and radioactive materials in various fields, the study of attenuation and absorption of X-rays and gamma-rays in several materials has become an essential and interesting field of research. Glass materials are possible alternatives of concretes for radiation-shielding materials. Materials and Methods: The mass attenuation coefficients (µm), effective atomic cross section (σa), effective atomic number (Zeff) and effective electron density (Neff) of silicate glasses containing different concentrations of Bi2O3, PbO, and BaO (30–70% by weight) were obtained using MCNP-4C code, XCOM and XMuDat programs, in the energy range of 10 keV–10 MeV. The interpolation method was employed to extract Zeff and Neff. The Auto-Zeff software was used to determine the Zeff as well. Results: The MCNP-4C Code, XCOM and XMuDat programs and Auto-Zeff results were in good agreement. It was found that the µm and σa values decrease with photon energy. Also the results indicate that σa and Zeff of glasses improve by increasing their Bi2O3, PbO and BaO contents, while increasing these contents to the same fraction has no significant effect on µm in the energy range of 0.3–5 MeV, where the Compton Effect takes over as dominant process and Neff do not follow certain rule. Above 0.1 MeV, lead oxide silicate glass showed the highest values of Zeff and σa. Conclusion: Observed good agreement indicates that the chosen Monte Carlo code and computer programs may be useful to calculate the gamma-ray shielding characteristics of different glass systems, particularly in cases where no experimental data exist.

Optimization of a SPECT system for imaging of 90Y in liver using Monte Carlo method

Introduction: Acquiring a high quality image has assigned an important concern for obtaining accurate diagnosis in nuclear medicine. Detector and collimator are critical component of Single Photon Emission Computed Tomography (SPECT) imaging system for giving accurate information from exact pattern of radionuclide distribution in the target organ. The images are strongly affected by the attenuation, scattering, and response of the detector and collimator. Method and material: The Planar and SPECT scans of a Y90 point source and also an extended Cardiac- Torso(XCAT) computerized phantom with the experiment and simulated systems were prepared. The SIMIND Monte Carlo program was used for simulating Siemen’s dual head variable angle SPECT imaging system with 4 detectors and 10 collimators. After verification and validation of the simulated system, the similar scans of the phantoms were compared from the point of view of image quality for 4 scintillator crystals including: NaI(Tl), BGO, LuAG: Ce, LaBr3 and also 10 collimators: Pb, Pb-Sb, Pb-Sb3, Pb-bi-Sn19, Pb-bi Sn375, Pb-bi-Sn50, Pb-bi-Sn-cd10, Pb-bi-Sn-cd125, Pt and Pt-Co. The parameters of energy and spatial resolution, and sensitivity of the systems were compared. Images were analyzed qualitatively by two nuclear medicine specialists. RESULTS: FWHM of the mentioned crystals and collimators obtained where: NaI (Pb, 0.3853) and BGO (Pb-Sb, 0.406), (Pb-Bi-Sn375, 0.405), (Pb-Bi-Sn-cd125, 0.375), and LuAG: Ce crystal (Pb-Sb, 0.425), (Pb- Bi-Sn19, 0.407), (Pb-Bi-Sn375, 0.417) and also LaBr3 (Pb-Bi-Sn375, 0.407), (Pb-Bi-Sn50, 0.430), (Pt-Co, 0.355). Medical diagnosis of the SPECT images of the phantom showed that the system with NaI(Tl)and LaBr3 by Pb-Sn3 collimator potentially provides a better detectability for hot lesions in the liver of XCAT phantom. CONCLUSIONS: The results showed that crystal NaI(Tl)and LaBr3 by Pb-Sn3 collimator has a high sensitivity and resolution, and also provides a better lesion detectability from the point of view of image quality on XCAT phantom.

A method for determining the angular distribution of atmospheric muons using a cosmic ray telescope

A cosmic ray telescope consisting of two scintillators (each one with a surface area of 0.14 m2, spaced 283 cm top of each other) was constructed to study the angular distribution of atmospheric muons. Using the CORSIKA code, the muons energy spectrum is parameterized in different energy regions at Tehran’s altitude (1200 m above sea level ≡897gcm−2), and by using a Monte Carlo program, the minimum energy recorded by the telescope is calculated. Due to the geomagnetic field, in the azimuth angle distribution of atmospheric muons, an anisotropy is observed in the East–West direction. The zenith angle distribution of the atmospheric muons follows the function cosnθ. Due to the relatively large field of view of the telescope, the iteration method is used to obtain the effective angle of orientation of the telescope. With this method, the value n=2.33±0.11 is calculated. The simulation data also provides the mean value n̄=2.30±0.10, which has a good match with the experimental result.

High-temperature reactor for hydrogen productions - a step towards future green energy

This article presents review of technology of high-temperature gas reactors and is features. In addition, it contains description of simple computation of neutron-physical characteristics of high-temperature reactor using GETERA and COMSOL Multiphysics programs and comparison of results with results obtained by precision Monte-Carlo program MCU.

Backscattered Electrons Spectra and Angular Distributions: Simulations with EGS5

The purpose of the present study is to compare numerical Monte Carlo simulations of backscattering of electrons, mainly in the keV range, with available experimental data. The final goal is to assess the ability of the Monte Carlo code to predict viable results, in view of the complexity and difficulty of performing experimental measurements. A specific code for simulating electrons backscattering was developed, based on the EGS5 electron-photon transport routines. The code was parallelized very efficiently for a common memory configuration. Simulation results for the backscattering coefficient h, the energy spectrum dh/dq, and the angle dependent energy spectrum dh/dqdW were obtained. Comparing with experiments shows agreement from very good to fair, especially in regions of high q (energy) values. For low values of q there are not experimental results due to difficulties in measurements. Hence, the Monte Carlo program can provide good estimates, in the range of energies from tens of keV up to 100-200 keV.

Backscattered Electrons Spectra and Angular Distributions: Simulations with EGS5

The purpose of the present study is to compare numerical Monte Carlo simulations of backscattering of electrons, mainly in the keV range, with available experimental data. The final goal is to assess the ability of the Monte Carlo code to predict viable results, in view of the complexity and difficulty of performing experimental measurements. A specific code for simulating electrons backscattering was developed, based on the EGS5 electron-photon transport routines. The code was parallelized very efficiently for a common memory configuration. Simulation results for the backscattering coefficient h, the energy spectrum dh/dq, and the angle dependent energy spectrum dh/dqdW were obtained. Comparing with experiments shows agreement from very good to fair, especially in regions of high q (energy) values. For low values of q there are not experimental results due to difficulties in measurements. Hence, the Monte Carlo program can provide good estimates, in the range of energies from tens of keV up to 100-200 keV.

Anomalous quartic gauge couplings and unitarization for the vector boson scattering process pprightarrow W^+W^+jjXrightarrow ell ^+nu _ell ell ^+nu _ell jjX

Weak vector boson scattering (VBS) at the LHC provides an excellent source of information on the structure of quartic gauge couplings and possible effects of physics beyond the SM in electroweak symmetry breaking. Parameterizing deviations from the SM within an effective field theory at tree level, the dimension-8 operators, which are needed for sufficiently general modeling, lead to unphysical enhancements of cross sections within the accessible energy range of the LHC. Preservation of unitarity limits is needed for phenomenological studies of the VVjj events which signify VBS. Here we develop a numerical unitarization scheme for the full off-shell VBS processes and apply it to same-sign W scattering, i.e. processes like qqrightarrow qqW^+W^+. The scheme is implemented within the Monte Carlo program VBFNLO, including leptonic decay of the weak bosons and NLO QCD corrections. Distributions differentiating between higher dimensional operators are discussed.

The attitudes of students towards the use of ICT during their studies

The purpose of this study was to examine attitudes of students towards the use of ICT during their studies. The survey included 285 students from Girne American University, Turkey. The sample consists of the students from first to fourth grade. The scale consists of 45 claims and is intended for determining students’ attitudes towards the use of ICT during their studies. Questionnaires were utilized to gather information on the attitudes of students towards the use of ICT during their studies. Information was broke down using SPSS statistical package (IBM SPS Statistics Version 20) and with Monte Carlo program for the parallel examination. The study established that students towards the utilization of ICT made the significant commitment to the students' academic performance. It is advanced that the discoveries of this study will be valuable to students to acquire knowledge into the ICT variables that influence students' scholastic execution and consequently enhance their academic performance.Results indicate that after one year of the intervention, there were statistically significant differences between the two groups only in sight vocabulary (at kindergarten and grade 1) and in alphabet (kindergarten). In all other areas of language development, there were no statistically significant differences between the achievement scores of the two groups. Results show that students appear to react to the prerequisites of their courses, programs, and universities. In all cases, there is a reasonable relationship between the students' view of handiness on certain ICT assets the critical quantities of understudies are quick to see ICT misused in the educating and learning process. There is positively scope for further research to examine how ICT interfaces crosswise over various areas and how the cross-connection application impacts its utilization.

Least Squares Monte Carlo and Approximate Linear Programming: Error Bounds and Energy Real Option Application

Least squares Monte Carlo (LSM) is an approximate dynamic programming (ADP) technique commonly used for the valuation of high dimensional financial and real options, but has broader applicability. It is known that the regress-later version of this method is an approximate linear programming (ALP) relaxation that implicitly provides a potential solution to a familiar ALP deficiency. Focusing on a generic finite horizon Markov decision process, we provide both theoretical and numerical backing for the usefulness of this solution, respectively using a worst-case error bound analysis and a numerical study dealing with merchant ethanol production, an energy real option application, based on an ALP heuristic that we propose. When both methodologies are applicable, our research supports the use of regress-later LSM rather than this ALP technique to approximately solve intractable Markov decision processes. Our numerical findings motivate additional research to obtain even better methods than the regress-later version of LSM.

Evaluation of neutron shielding properties of steel slag waste

The present work attempts to increase the benefit of using calcium fluoride based slag, which considers as waste material after remelting of advanced steel by an electro slag remelting (ESR) process, as one of innovative material for nuclear shielding applications. This work differentiates between the neutron shielding properties of different types of steel slag waste, types of stainless steel and ordinary concrete. The total and partial neutron interactions have been done in the energy range of 10−5 eV–20 MeV using Monte Carlo program. The dependence of total and partial neutron macroscopic cross sections (MaCSs) on incident neutron energy and elemental composition has been evaluated. Besides, the total and partial microscopic cross sections (MiCSs) were determined via the total and partial MaCSs. It was found that the rutile has higher total MaCSs and MiCSs than the other investigated materials. This study should be useful for potential application of these materials in the field of nuclear radiation for choice of neutron shielding materials.

Z0 +jet correlation with next-to-leading-order-matched parton-shower and jet-medium interaction in high-energy nuclear collisions

The impact of jet quenching on $Z^0$-tagged jets in relativistic heavy-ion collisions at the Large Hadron Collider (LHC) is investigated. We employ Sharpa Monte Carlo program that combines next-to-leading order matrix elements with matched resummation of parton shower to compute the initial $Z^0$+jet production. The Linear Boltzmann Transport (LBT) model is then used to simulate the propagation, energy attenuation of and medium response induced by jet partons in the quark-gluon plasma. With both higher-order corrections and matched soft/collinear radiation as well as a sophisticated treatment of parton energy loss and medium response in LBT, our numerical calculations can provide the best description so far of all available observables of $Z^0$+jet simultaneously in both p+p and Pb+Pb collisions, in particular, the shift of the distribution in transverse momentum asymmetry $x_{\rm jZ}=p_T^{\rm jet}/p_T^Z$, the modification of azimuthal angle correlation in $\Delta\phi_{\rm{j}Z}=|\phi_{\rm jet}-\phi_Z|$ and the overall suppression of average number of $Z^0$-tagged jets per boson $R_{\rm jZ}$ at $\sqrt s =5.02$ TeV as measured by the CMS experiment. We also show that higher-order corrections to $Z^0$+jet production play an indispensable role in understanding $Z^0$+jet azimuthal angle correlation at small and intermediate $\Delta\phi_{\rm jZ}$, and momentum imbalance at small $x_{\rm jZ}$. Jet quenching of the sub-leading jets is shown to lead to suppression of $Z^0$+jet correlation at small azimuthal angle difference $\Delta\phi_{\rm jZ}$ and at small $x_{\rm jZ}$.

A coupled rate theory-Monte Carlo model of helium bubble evolution in plasma-facing micro-engineered tungsten

A multiscale model of helium bubble evolution in plasma-facing materials is developed. The model links different stages of helium bubble evolution: deposition, nucleation, growth, motion, and coalescence. Helium deposition is simulated with the SRIM Monte Carlo program to give spatial information on helium and displacement damage distributions near the surface. This deposition profile is then introduced into a space-dependent rate theory of bubble nucleation and growth to describe the early stages of the distribution and size of helium bubbles. The coarsening stage of bubble evolution as a result of whole bubble motion, interaction, and coalescence is modeled by a new Object Kinetic Monte Carlo (OKMC) model, for which initial conditions are taken from the mean-field rate theory calculations. The model is compared to experimental data on low-energy helium plasma interaction with micro-engineered tungsten (W), and on high-energy helium ion deposition in flat W samples. Novel features of the multiscale model include: (1) space-dependent rate theory; (2) OKMC model of bubble motion in stress and temperature fields; and (3) application of the model to micro-engineered materials, and comparison with experiments on the same time-scale. At low helium ion energy, it is found that the mechanism of trap mutation is essential in achieving good agreement with experimental measurements. On the other hand, good agreement with experiments at high incident ion energy and temperature showed the importance of bubble coalescence and coarsening as main mechanisms. The results of the model are compared with experiments on flat W surfaces irradiated at high ion energy (30 keV), and with micro-engineered W, where the surface is coated with high-density micro-pillars at low ion energy (around 100 eV). The predicted average bubble radius and density are in qualitative agreement with experimental results.

Kinematics Analysis and Workspace Calculation of a 3-DOF Manipulator

Robot working space is an important kinematic indicator. Exact computation of the boundary shape and volume or area of the manipulator workspace is very important for its optimum design and application. This paper describes the kinematics analysis of a 3-DOF manipulator and the calculation of its workspace. The kinematics model of the three degree of freedom (3-DOF) robot was set up with the D-H parameters method. The effectiveness of kinematics equations was verified by the Robotics Toolbox simulation of the MATLAB. The robotics workspace of the manipulator was analyzed and simulated based on the Monte-Carlo method and MATLAB software programming. The analysis results show that the manipulator’s working space is well-knit and this method is feasible and practical, prove the trajectory planning of workspace, and can well perform task, which lay a foundation to further study of the trajectory planning and motion control.

Superior signal persistence of circularly polarized light in polydisperse, real-world fog environments.

We present simulation results quantitatively showing that circularly polarized light persists in transmission through several real-world and model fog environments better than linearly polarized light over broad wavelength ranges from the visible through the infrared. We present results for polydisperse particle distributions from realistic and measured fog environments, comparing the polarization persistence of linear and circular polarization. Using a polarization-tracking Monte Carlo program, we simulate polarized light propagation through four MODTRAN fog models (moderate and heavy radiation fog and moderate and heavy advection fog) and four real-world measured fog particle distributions (Garland measured radiation and advection fogs, Kunkel measured advection fog, and Sandia National Laboratories' Fog Facility's fog). Simulations were performed for each fog environment with wavelengths ranging from 0.4 to 12µm for increasing optical thicknesses of 5, 10, and 15 (increasing fog density or sensing range). Circular polarization persists superiorly for all optical wavelength bands from the visible to the long-wave infrared in nearly all fog types for all optical thicknesses. Throughout our analysis, we show that if even a small percentage of a fog's particle size distribution is made up of large particles, those particles dominate the scattering process. In nearly all real-world fog situations, these large particles and their dominant scattering characteristics are present. Larger particles are predominantly forward-scattering and contribute to circular polarization's persistence superiority over broad wavelength ranges and optical thicknesses/range. Circularly polarized light can transmit over 30% more signal in its intended state compared to linearly polarized light through real-world fog environments. This work broadens the understanding of how circular polarization persists through natural fog particle distributions with natural variations in mode particle radius and single or bimodal characteristics.

Water-equivalence of ZrO2 doped polystyrene by Monte Carlo simulation

Objective To design water-equivalent plastic scintillator detector for the measurement of absorbed dose in tumor radiotherapy. Methods The concentration of ZrO2 to be doped in polystyrene was estimated according to the empirical formula, and then the Monte Carlo program Geant4 (GEometry And Tracking 4) was used to simulate the energy deposition and transport process of X-rays with different energies in water, solid water RW34 (composed of 2.1 wt% TiO2 doping polystyrene) and different concentrations of ZrO2 particles doped in polystyrene. The dose and attenuation coefficients were compared among different materials at different depths of water. Results The doses at different depths and the attenuation coefficient of polystyrene (doped with about 0.4 wt% ZrO2 nanoparticles) were much more consistent with those of water and even exhibit much better water-equivalence than RW34. Conclusions The simulation results provide the basis for the development of water-equivalent scintillator. Key words: Geant4; Water-equivalent; ZrO2nanoparticle; Polystyrene

Neutronics analysis of the ITER Collective Thomson Scattering system

The Collective Thomson Scattering (CTS) will be the ITER diagnostic responsible for measuring the alpha-particle velocity distribution. Using mirrors, a powerful microwave beam is directed into the plasma via an opening in the plasma-facing wall. The microwaves will scatter off fluctuations in the plasma, and the scattered signal is recorded after transmission through a series of mirrors and waveguides. Several components of the CTS system will be directly exposed to neutron radiation from the plasma which can change the properties of the components and reduce their lifetime. In this paper, a neutronics analysis is presented for the CTS system. A study on the influence of different materials on the nuclear heat loads in the launcher mirror is also presented, along with the design of a simple cooling system. All the studies were conducted using the Monte Carlo program MCNP6. The outputs, in particular the nuclear heat loads, will be used to perform the thermal analysis of the system.

Determining the gamma-ray parameters for BaO–ZnO–B2O3 glasses using MCNP5 code: a comparison study

ABSTRACTRapid technological advancement has multiplied people’s exposure to ionizing radiations greatly. Widespread applications of radiation in different fields (such as agriculture, radiation therapy and scientific research fields) require that humans be protected against unnecessary exposure. In this study, mass attenuation coefficient (μm), half-value layer, mean-free path, effective atomic number (Zeff) and exposure buildup factor have been calculated for xBaO–20ZnO–(80 − x)B2O3 (x = 5, 10, 15, 20 and 25 mol%) glass systems. The mass attenuation coefficients of the selected glasses were calculated using simulation method of MCNP5 code. The simulation results have been compared with the experimental data and Xcom at the energies 223.02, 252.98, 287.28, 340.83, 398.97, 481.59, 562.68 and 662.00 keV. The agreement amounts of the mass attenuation coefficient values are from 0.2% to 2.8% and from 0.2% to 6.98% for MCNP5 and Xcom relative to experimental results, while the Monte Carlo program values are higher than that obtained by experimental data, using Xcom and MCNP5 code. The glass sample having the highest value of BaO content show high radiation shielding properties. It indicates that the MCNP5 code can be used for estimation of radiation interaction parameters where experimental results are not available.

Image quality assessment with dose reduction using high kVp and additional filtration for abdominal digital radiography

PurposeDose reduction using additional filters with high kilovoltage peak (kVp) for abdominal digital radiography has received much attention recently. We evaluated image quality with dose reduction in abdominal digital radiography by using high kVp and additional copper filters at a tertiary hospital. MethodsBetween June 2016 and July 2016, 82 patients underwent abdominal digital radiography using 80 kVp in X-ray room 1 and 82 were imaged using 92 kVp with 0.1-mm copper filtration in X-ray room 2. The effective dose was calculated using a PC-based Monte Carlo program. Image quality of the abdominal radiography acquired in the two rooms was evaluated using a five-point ordinal scale, as well as the signal-to-noise and contrast-to-noise ratios. ResultsThe mean effective dose decreased by 25.8% and 25.7% for the supine and standing positions, respectively, when abdominal digital radiography using 92 kVp with 0.1-mm copper filtration was performed. In the 20 patients who performed abdominal digital radiography twice in each room, visual grading scores for visualisation of psoas outlines and kidney outlines are higher in room 1. However, there was no statistical significant difference of visual grading scores among the 124 patients who underwent only one abdominal radiography in the room 1 or 2 (P > 0.05). ConclusionsDose reduction for abdominal digital radiography can be achieved with comparable image quality by performing abdominal digital radiography using 92 kVp with 0.1-mm copper filtration, despite the higher AEC dose.

Pumping Performance Evaluation of HL-2M In-Vessel Cryopump With Monte Carlo Method

Sufficient pumping speed and good pumping performance should be guaranteed for the HL-2M tokamak. In order to provide sufficient pumping capacity, two in-vessel cryopumps will be installed at outer floor and ceiling, respectively. Pumping performance of HL-2M in-vessel cryopump has been estimated by direct simulation Monte Carlo program and test particle Monte Carlo program under free molecular flow condition. The predicted pumping speeds of each bare cryopump are 51.29 m3/s for H2, 38.04 m3/s for D2, and 24.94 m3/s for He. An advanced divertor system will be installed, located on the floor of the HL-2M vessel. When the conductance of the divertor is taken into account, the pumping speeds of the floor ring are 20.11 m3/s for H2, 15.14 m3/s for D2, and 12.50 m3/s for He. This shows that the effective pumping speed of the cryopump is greatly affected by the conductance of the divertor. A parametric study has been carried out, allowing the sticking coefficients of some different gases to vary within a +/−0.05 range with respect to the corresponding reference values. The results indicate that the He pumping speeds may be significantly affected by a small change of the sticking coefficient, while negligible effects are predicted to occur, as far as H2 and D2 are concerned. The results of the dynamic evaluation of the pumping process indicate that the cryopump has a quick time response.